Switch mounting arrangement



July 16, 1968 A. F. HUBBARD 3,392,778

SWITCH MOUNT ING ARRANGEMENT Filed Aug. 5, 1966 I NVENTOR.

4rzhur E 144/6 bard United States Patent O" 3,392,778 SWITCH MOUNTINGARRANGEMENT Arthur F. Hubbard, Moline, [1]., assignor to American AirFilter Company, Inc., Louisville, Ky., a corporation of Delaware FiledAug. 5, 1966, Ser. No. 570,510 2 Claims. (Cl. 165-39) The presentinvention relates to heat-responsive switches and more particularlyrelates to mounting arrangements to improve the effectiveness andreliability of heat-responsive switches adapted for use in portable airheating devices.

Previous air heating devices have included thermal responsive switchesat various locations in the air flow path to sense the temperature ofthe air passing through the heating device and control selected elementsof the heating device in response to the temperature sensed by theswitch. In some applications, particularly where the switches aremounted adjacent a heat exchanger, combustion chamber or on a coldsurface, such heat-responsive devices have not operated in response tothe actual average temperature of the air stream flowing through theheating device and the operation has been unsatisfactory.

In accordance with the present invention, an arrangement is providedwhereby a temperature-responsive switch can be mounted at any selectedlocation in the air stream in a portable heater and the switch wllloperate satisfactorily in response to the changes in the temperature ofthe air stream regardless of the proximity to the combustion chamber,heat exchange means or other elements of the air heating device.Furthermore, it has been recognized that the new, advantageous, andinexpensive switchmounting arrangement in accordance with the presentinvention provides means to assure that the temperature sensed by theswitch is the actual average temperature of the air stream passing theswitch.

Various other features of the present invention will become obvious toone skilled in the art upon reading the disclosure set forthhereinafter.

More particularly, the present invention provides an improved mountingarrangement for a temperature responsive switch in an air heatercomprising: thermal insulating means fixed to a wall of the air heatingdevice which defines at least a part of an air flow path through theheater; heat conductive fin means having a first portion mounted ininsulated relation with the wall by means of the thermal insulatingmeans, and a second portion extending transversely into the air streamflowing past the wall; and heat responsive switch means mounted ininsulated relation with the wall and contacting the first portion of thefin means in contiguous heat-conductiverelation.

It is to be understood that various changes can be made in thearrangement, form, and construction of the apparatus disclosed hereinwithout departing from the scope or spirit of the present invention.

Referring now to the drawings:

FIGURE 1 shows a view, partly in section, of an example of a portableheater having a switch mounting arrangement in accordance with thepresent invention;

FIGURE 2 is an enlarged view taken along a plane passing through line 22of FIGURE 1; and

FIGURE 3 is a view taken along a plane passing through line 33 of FIGURE2.

The switch mounting arrangement in accordance with the present inventioncan be used in a portable air heater and the portable heater shown inFIGURE 1 includes a temperature responsive switch 16 mounted in airpassage 7. Switch 16 can be mounted at a selected location in theportable heater to control the operation of selected elements of theheater, for example, safety devices which 3,392,778 Patented July 16,1968 terminate operation of the heater upon the occurrence of selectedconditions.

In the example of the air heater shown in FIGURE 1, air is drawn intothe heater through an air inlet 17 by fan 6 driven by motor 9 and ashroud 18 is provided to direct the flow of air. The heater includescombustion chamber 1 defined by an outer casing 13 and end walls 11 and23 and a fuel burning combustor 24 to provide a source of heat for theheater. Hot gases generated in combustor 24 pass out of combustionchamber 1 through a hot gas conduit 8 into annular heat exchanger 2 andare emitted from heat exchanger 2 by means of vent stack 10. Air to beheated is blown through annular passages 7 and 7a defined be-tweencasing 13 of combustion chamber 1 and surface 14 of heat exchanger 2.and between surfaces 15 of annular heat exchanger 2 and casing 19,respectively. The heated air is emitted from outlet 31 of the portableheater to an adjacent space to be heated.

Combustion air for burner 34 is supplied from chamber 20 definedgenerally by casing 13 and end walls 23 and 25. Such air is supplied tochamber 20 by fan 6 through an auxiliary combustion air duct (notshown). Fuel can be supplied to combustor 24 by means of a fuel line 21and electricity is provided by means of electrical wires 22 to ignitethe fuel in the combustor 2.4.

In accordance with the present invention a new and improved temperaturesensing arrangement is provided and includes (FIGURE 2) atemperature-responsive heat switch 28 and heat conductive fin 27fastened to casing 13 by bolts 29. Temperature-responsive switch 28 canbe mounted through an aperture 32 of fin 27 and is in contiguousheat-conductive relation with fin 27. A layer 26 of insulating materialis provided to separate heat conductive fin 27 .and the bottom of switch28 from casing 13, the base of the switch extending laterally outward tonest between fin 27 and layer 26. In the example of FIGURE 1, switcharrangement 16 is mounted on casing 13 adjacent the combustion airsupply chamber 20. In operation of the switch in the locationillustrated in the example of the present invention, casing 13 becomesextremely hot in the area adjacent combustion chamber 1 and the heat isconducted to the portion of casing 13 adjacent chamber 20. It is to benoted that if switch 16 were mounted directly on casing 13 instead of oninsulating layer '26, heat conducted to switch 28 would increase thetemperature of the switch and would accordingly decrease the sensitivityof the switch to changes in temperature of the air stream so operationof the switch would be adversely affected. In accordance with thepresent invention fin 27 includes a second portion 27a which is directedtransversely into the stream of air flowing through passage 7. It hasbeen recognized that fin 27 induces turbulence in the stream of airflowing past casing 13 and mixes the air stream in passage 7 so thetemperature of the mixture is the average of the temperatures acrosspassage 7. Pin 27 can advantageously be directed upstream relative tothe air flow so that the air stream is mixed downstream to the fin andthe mixed stream flows over switch 28 to expand switch 28 to the averagetemperature of the air stream. Moreover, in accordance with the presentinvention, it has been recognized that fin 27 is heated, or cooled, tothe average temperature of the air flowing through passage 7 and switch28 is heated or cooled accordingly. Because the bottom side of switch 28is insulated from casing 13, switch 28 is exposed only to the averagetemperature of the stream of air flowing through passage 7 and theaccuracy and operating efiiciency of temperatureresponsive switch 28 issignificantly improved.

It will be noted that switch 28 includes a heat-responsive temperaturesensing surface 28a (FIGURE 3) which operates the switch at selectedtemperature in the air stream and the resulting signal can betransmitted to a selected control element by suitable means, forexample, wire 30.

In previous heaters, heat-responsive switches have been used to actuatesafety and control devices included within the heater and such switcheshave been mounted directly to the wall of casing of the heat exchanger,combustion chamber, or the outer casing of the air heater. Such previousarrangements have been unsatisfactory because the switches have beenmore affected by the condition of environment in which they are mountedthan the temperature of the air stream. Such switches, therefore, havenot effectively responded to changes in temperature of the air streamflowing past the switch. In some applications such switches have beenused to determine undesirable over-heating in certain areas of portableheaters as indicated by unusually high temperature in the air stream andin other applications such switches have been provided to react tosubnormral temperatures to indicate the flame has been extinguished inthe combustion chamber. Temperature responsive switches mounted inportable air heaters in accordance with the combination of insulatinglayers and fin arrangements provided by the present invention operateefiiciently in either application.

The invention claimed is:

1. An improved mounting arrangement for temperature-responsive switchesin an air heater comprising: thermal insulating means joined to a wallof an air flow 4. conduit of an air-heating device; heat-conductive finmeans having a first portion connected to said thermal insulating meansand said wall means and a second portion extending into the air streamflowing through said conduit past said wall; and heat-responsive switchmeans joined to said first portion of said fin means in contiguousheat-conductive relation to operate selected elements of said airheater.

2.- The apparatus of claim 1 wherein said second portion of said finmeans extends into said air stream in an upstream direction relative tothe direction of air flow through said conduit from said temperatureresponsive switch means, where said first portion of said fin meanssurrounds said switch means and is mounted over a laterally-extendingbase of said switch, said base means also being mounted on said thermalinsulating means.

References Cited UNITED STATES PATENTS 2,451,903 10/ 1948' Bauman165--32 2,879,976 3/1959 Rose 165-122 3,329,140 7/1967 Hubbard 165-185ROBERT A. OLEARY, Primary Examiner. CHARLES SUKALO, Examiner.

1. AN IMPROVED MOUNTING ARRANGEMENT FOR TEMPERATURE-RESPONSIVE SWITCHESIN AN AIR HEATER COMPRISING: THERMAL INSULATING MEANS JOINED TO A WALLOF AN AIR FLOW CONDUIT OF AN AIR-HEATING DEVICE; HEAT-CONDUCTIVE FINMEANS HAVING A FIRST PORTION CONNECTED TO SAID THERMAL INSULATING MEANSAND SAID WALL MEANS AND A SECOND PORTION EXTENDING INTO THE AIR STREAMFLOWING THROUGH SAID CONDUIT PAST SAID WALL; AND HEAT-RESPONSIVE SWITCHMEANS JOINED TO SAID FIRST PORTION OF SAID FIN MEANS IN CONTIGUOUSHEAT-CONDUCTIVE RELATION TO OPERATE SELECTED ELEMENTS OF SAID AIRHEATER.